Bone conduction heabing-aid



June 20, 1944. H. LIEBER Re. 22,499

BONE CONDUCTION HEARING-AID Original Filed Deo. 24, 1932 Raiatea June zo, 1944 sans v nous coNnUc'rroi'v uname-Am Hugo Lieber, deceased, late of New York, N. Y., by

Lieber,` Patents Corporation, assignee, Elmsford,

Original No. 2,077,425, dated April 20, 1937, Serial No. 348,733. December 24, 1932. Renewed Febmary 28, 1934. Application for reissue April 14, 1939. Serial No. 237,932

comme (ci. 11a-1m This invention relates to bone conduction hearing-aids. and it has among its objects an improved bone conduction receiver of small size and light weight suitable. for inconspicuous wear by the user and able to impart -to the bone structure of a hard of hearing person the vibratory energy required for inducing hearing in his auditory nerve center.

Theioregoing and other objects of the invention will be best understood from the following description, reference being made to the accomf panying drawing, in which l Fig. 1 is a view of the vibrator element illustrating how a bone conduction receiver of the invention may be held against the bone structure of the upper portion of the spinalcolumn of a person .hard-of-hearing;

Fig. 2 is a, circuit diagram of a hearing-aid device;

Fig. 3 is a vertical sectional view through the bone conduction receiver along line 3-3 of Fig. 4:

Fig. 4 is a vertical sectional view of the receiver along line l-i of Fig. 3;

Fig. 5 is a horizontal sectional view`through the receiver along line 5-5 of Fig. 4;

Fig. 6 is a top view and Fig.' '7 is a cross sec- I tional view of the pole plate of the receiver;

Figs. 8 andr 9 are vertical sectional views similar to Fig. 3 of the center portion of a receiver embodying modications of the invention.

Although it has been known for many years that a large percentage oi persons with impaired hearing have satisfactory interior hearing organs and that they are able to hear well by bone conduction, prior bone conduction hearing devices or receivers proved impractical because they were all large and cumbersome and could not be made small enough for inconspicuous wear by the user.

As shown by Kranz Patent 1,540,783, it has also' been well known that electromagnetic bone conduction receivers have to Abe provided with a rela- 'tively stiif diaphragm so that when it is actuated by an electromagnet which is energized with speech frequency oscillations, the diaphragm vibrates with large forces and small amplitudes required in order to impart to the hearing inducing bones of the user the vibratory energy required to induce satisfactory hearing of speech 5 by bone conduction.

for comfortable and inconspieuous wear coupled to a hearing, inducing bone or the user. and having an overall mass of onlyl about 16 grams and an overall volume of only about 7 cubic centimeters, is designed and arranged to operate elllciently with a resonance in the speech frequency range of about'1000 cycles so as to enable the user to hear speech intelligibly by bone conduction, even when used in a standard hearing aid circuit formed of a conventional hearing aid ampliiier, battery and microphone, all designed for hidden and nconspicuous wear on the body of the user.

'I'he hearing-aid bone receiver unit of the pres- .ent invention comprises a driving portion and a driven portion and intermediate relatively stil! elastic elements interconnecting said driving and driven portions so as to permit a limited vibratory movement between the driving and driven portions throughout the principal speech frequency range under the action of corresponding electric oscillations applied thereto. 'A casing which forms part of thevibratory bone-receiver unit is secured to the driving portion, and the driven portion has secured thereto a contacter arranged for engaging the bone structure of the user. The contacter forms part of a wall of the casing which has lateral dimensions suiliciently extended and so arranged under the vibratory unit as to malntain it in a stable equilibrium coupling position on the bone structure under 'a relatively small external -force, the bone receiver unit being provided with supporting means mechanically coupled to its driving portion for holding its driven portion with the contactor in engagement with the bone of the user so that the contacter may vibrate relatively to said driven portion and the supporting means when the unit is energized for transmitting vthe vibrations of the contacter through the bone structure tothe inner ear. The` mass of the driving portion is only a small fraction of the mass of the body of the bone structure against which it is held, and suillciently` large and sufficiently actuated by the electric means as to impart tothe driven portion and through its contacter to the bone the vibratory energy required for inducing intelligible hearing In applicant's copending application Serial No.

614,674, iiled June 1, 1932, Patent 1,940,553, there is disclosed a novel wearable hearing-aid bone receiver of applicants invention, in ,which a viof speech by bone conduction.

Fig. 1 illustrates a hard-of-hearing person hav- 0 ing a bone conduction receiver 2l of the invention held pressed against a spinal column bone by means of a light harness of flexible straps 22, the receiver being connected through a ilexible double conductor cord 23 with the associbrating mechanism unit light and small enough ated elements, in accordance with the diagram conduction receiver 2l as ln similar air conduc-V tion hearing-aids.

The bone conduction receiver 2| is shown in detail in Figs. 3 to 'l and comprises a casing l2 within which is mounted an electromagnetic vibrator core structure comprising a central core 34 surrounded by the actuating coil Il and two L-shaped permanent magnets 3l so as to produce with the pole plate Il, shown in detail in Figs. 6 and '1, a flux inthe annular gap between the core and the pole plate. i

Mounted above the pole plate within the casing opening is a diaphragm unit Il comprising a circular resilient sheet-metal diaphragm l2 held radially tensioned by a tension ring Il.' The tension ring may be, for instance, made from a split ring of larger diameter compressed to the diameter of the diaphragm and soldered to tbe edge thereof so that under the action of the e forces tending to restore the ring to its original position. a uniform radial tension is applied to the diaphragm.

To the imderslde of the diaphragm is' secured. as by soldering. a flat circular armature Il of soft iron. The lower surface Il of the armature Il is parallel to the polefaces of the central core member Il and the pole plate Il and is spaced therefrom by a small gap It to provide a path forthe permanentflux of the magnets 3l andofthe induced flux of coil 3i. The diaphragm Y unit isheldflrmlyinplacewithinthecasingbymeans of a locking ring it which is screwed in within the threaded upper end of the interior casing wail, thin washers Il serving to properly space the diaphragm unit with respect to the lpole faces 35 and II. Y 4

The open side of thecasing isclosedbyacover il mounted on an external threaded portion of the casing, and a lock nut ring-II serves to lock the cover in the desired operating Pitlon. The central portion ofthe cover ll has a central cylindrical opening Il for guiding a contact button $6 mounted on a rod il extending from the center ofthe armature Il. The contact button 66 may be mmmted in place before inserting the cover by placing it with its central hole over the upper projection of the rod l1 and soldering the two together at the top end, a thin cap il, of a nonoxidizing material, for instance. gold, being soldered over the top of the Junction to form the exterior contact surface of the button Il.

The outer side of the central enlargement Il of the cover' l0 forms a supporting surface Il around the contact button II. When the bone 1 receiver shown is held in a released condition.

free from engagement with the bone structure. the outer surface il of the contact button projects slightly above the supporting surface l of the casing coveras shown in Fig. 4. When the vibratory unit forming the bone receiver is held in its operative position on the bone, and is actuated by electric oscillations of the principal speech frequency range, its massive driving portion which is formed by the relatively heavy magnetic structure with its energizing windings 3l and the mainvpart of the casing I2 is supported by the elastic diaphragm I2, at a small magnetic gap spacing from the armature Il and the contactor Il which is secured thereto, and which form the'driven vibratory portion which acts on the bone structure. The contactor BI forms part of the casing wall Il, which is so arranged under the driving vibratory portion as to maintain the contactor and the entire vibratory unit in an eiilcient stable equilibrium coupling position on-the bone when it is held against it by a support which is pivotally connected to the casing and applies thereto only a relatively small external force. The mass of the driving portion, although only a small fraction of the mass of the body of the bone structure. is sumciently large and is sumciently actuated by the electric oscillations as to impart to the driven vibratory portion and through its contactnr Il to the bone the vibratory energy re-I quired for inducing intelligible hearing of speech by bone conduction. f

the armature to the outer periphery thereof, and v therefrom back through the gap to the outer pole face Il of the pole plate Il and therethrough to the oppomte poles of the L-shaped magnets, a part of the flux being also induced by the steady` current lilowing through the coil Il from the battery 2|. This flux will tend to pull the armature il towards the pole faces underneath, but

the diaphragm 52 is made suillciently stili' to oppose this magnetic pull and to keep it in the position where the contact button projects above the supporting surface I9, as shown in Fig. 4'. On pressing the vibrator against the body, the contact surface il is pressed inwardly into the opening Il of the cover lmtil the outer contact surface Il of the button lies flush with the supportingsurface ls, as shown in Fig. 3, the body portion being indicated by line 1I. This brings the amature nearer to the pole pieces, decrees-L.

ing. the air gap. V

In accordance with one phase of the invention, the bone receiver shown is enabled to operate with a very small gap by arranging the contact button Il to project above the surrounding supiporting surface il of the casing when in released position as shown in Fig.- 4, and to be pushed into the casing, when it is pressed with the but-'- ton surface Il against the bone structure, till it reaches a position where the outer contact surface of the button is substantially ush with the adjacent supporting surface of the This small inwax'i motion of the button is -aocompanied by a corresponding small motion `of the diaphragm till the armature reaches a predetermined operating distance from Ythe pole faces beyond which it cannot be pushed by the button. This operating gap is made only little larger than the freezing gap distance so that the armature may vibrate in the region close toJ the gap zone in which it would be caused to freeze,

but, nevertheless, stay outside the freezing zone and vibrate under the action of the'normal flux fluctuations induced by the coil. By thus bringing the armature to a position where the gap is larger than the freezingzone and yet not too large, the vibrator is able to develop relatively large power in a structurel small enough to be inconspicuously worn on the body of the user. In the use of such vibrators, sound vibrations stronger than normal will often occur. In such cases the current iiowingthrough the actuating coil 3i may momentarily become so large as to increase the flux in the gap to a value at which the armature vibrating near the border of the normal freezing zone will be pulled over by the increased flux and become frozen notwithstanding that under normal operation no such pull over will occur. Such momentary freezing of the armature is quite frequent if the operating gap of the armature is made close to the freezing zone, and very little advantage would be gained by choosing such small gaps because once the armature is frozen to the pole faces, the circuit mustbe cut oi! and the vibrator shaken to set the armature out of the freezing position.

In accordance with the invention, this diiliculty is overcome to a substantial extent by preventing permanent freezing of the armature to the pole faces in the presence of excessive magnetic uxes in the gap. and instantaneous restoration of the vibrator to the non-freezing condition upon the disappearance and passing of excessive momentary magnetic fluxes. This is effected by attaching thin flat spacers 13, as by soldering, to the pole face I9 of the pole plate 38, these spacers being of non-magnetic material, for instance, brass, and stopping the downward movement of the armature at a distance before it contacts with the pole faces. With such spacers, a large magnetic force produced by a speech current impulse, although it might cause momentary pulling in of the armature into the freezing zone, will not be able to produce any permanent freezing of the armature, and the armature will be free to return to normal operating position.`

lIn the practical construction of a vibrator of the invention, satisfactory results may be obtained by limiting the inward movement of the contact button 66 so that in the position to which the button is brought by compressing it against the body, the operating gap between the-armature surface and the pole faces of the magnet core is about 3 to 4 mils. The stop members 13 should be of a thickness of about 1 to 2 mils and prevent the armature from coming near the pole faces closer `than that distance. A vibrator made to operate with such gap spacing and constructed in the way shown in Figs. 3 to I may be made to have an outside diameter 'of about 60 millimeters and a height of about millimeters, being thus inconspicuous and readily adapted for wear on the body of the user.

Exact adjustment of the normal operating position at which the contact surface of the button is flush with the surrounding supporting surface of the cover may be effected by turning the cover one way or another by means of ridge B2, the nut 63 serving t`o lock the cover in adjusted position.

Instead of securing the armature stops 13 to the pole face 49 of the pole plate 40,-these stops may be secured to the under-surface of the armature 54 as shown at 'I6 in Fig. 8, the stops being attached by soldering, for instance, and having a thickness of about 1 to 2 mils as before.

The novel combination of a bone conduction receiver with coupling means for imparting hearing-inducing vibrations to the vertebrae of the spinal column of a deafened person so as to enable him to hear without making his impairment conspicuous is claimed in copending the breadth of the appended claims 'they shall not be limited to the specic details shown and described in connection with the exemplications of theinvention.

What is claimed is:

l. In a portable bone conduction hearing-aid device, an electromagnetic bone conduction receiver of small size suitable for inconspicuous wear by the user comprising a magnetic core of substantial mass having a pole face, a casing enclosing said core, a magnetic armature resiliently supported by said casing ata gap spacing of the order of 2 mils adjacent said pole face, windings interlinked with -said core for inducing in said gap magnetic forces imparting soundfrequency vibrations to said armature across said gap, a cover for said casing having an opening facing said armature, a contact member extending from said armature having an external contact surface projecting through said cover opening for engaging hearing-inducing bone structure of the user, and resilient supporting means for carrying said receiver in a floating condition and pressing the contact surface of said contact member against hearing-inducing bone structure while said contact member is subjected to forces tending to freeze said armature to said pole face, and means for adjustably locking said cover in a position at which the portion of the cover adjacent said opening limits the inward movement of said contact member to a position in which said gap is maintained ata sumciently small length for producing by the action of the floating mass ofV said receiver hearinginducing vibratory forces imparted to said bone structure without freezing said gap.

2. In an audiphone. the combination of electromagnetic means adapted to respond to varying currents substantially throughout the audible frequency range, a casing secured thereto, a relatively stiff vibratory member operatively associated with the means for vibration thereby, a contactor connected to the member and forming at least part of a wall of the casing, resilient means between the contactor and the casing whereby the contactor can vibrate relatively'to the casing, and means supporting the casing with the contactor in operative contact with the bone Istructure of the user for conducting its vibrasaid portion of the other member for relatively vibrating the same, a contactor forming at least part oi a wall of the casing connected to the unsecured member for movement relatively to the casing in accordance with said vibration, and i means supporting said casing with said contactor in operative contact with' the bone structure o! the user for conducting its vibrations therathrough to the inner ear.

4. In an audiphone. the combination of a casing. vibrator means in the casing comprising two members having unequal inertias resiliently associated for limited relative movement between at least portions oi' both members. means securing the member having greater inertia to the casing. electromagnetic means adapted torespond to varying currents substantially throughout the audible frequency range secured to said portionot one of said members and operatively vopposed to said portion of the other member for relatively vibrating the same, a contactor forming at least part oi' a wall of the casing connected to the unsecured memberi'or movement relatively to the casing in accordance with said vibration, and i means supporting said casing with said contactor in operative contact with the bone structure oi the user for conducting its vibrations therethrough to the inner ear.

5. In an audiphone, the combination of a vibratory mechanism comprising two members.

relatively stiff spring means connecting said members permitting a limited relative movement between at least portions oi both members' electrical means adapted to respond to varying currents within the audible frequency range secured to said portion of one of said members and operatlvely opposed to said portion of the other member for relatively vibrating the same, a casing for said mechanism secured to one oi said members,v a contactor directly secured to one oi' said members for engaging the use r and forming at least part oi a wall of the casing, and supporting means firmly mechanically coupled to the member that lis not directly secured to the contactor for holding the said last named member substantially stationary with the contactor.

N1 bone so that the contactor vibrates relatively to in engagement with the bone structure ot the v user, whereby the contactor is tree to 'vibrate relatively to said last-named member and said supporting means when said electrical means is energized ior transmitting the'vibrations of the contactor through the bone structureto the inner ear. p

6. In a wearable bone conduction hearing aid device, a vibratory unit suihciently lighty and small enough for comfortable and substantially inconspicuous wear coupled to a hearing inducing bone structure of the user and comprising a driving portion, a driven portion and intermediate relatively-still elastic elements interconnecting said driving and driven portions so as to per- .mit a` limited vibratory movement between at least parts oi both portions; electrical Vmeans secured to one of said portions forv actuating said portions throughout the principal speech frequency range and producing corresponding vi,

brations -between said portions; a casing forming part of said unit and secured to said driving portion; a contactor directly secured to said driven portion lor engaging the bone structure ofthe user; said contactor forming at least part 22,499 i of a wall of said casing having a wall portion with lateral dimensions sumciently extended and so arranged under the driving portion as to maintain said vibratory unit in a stable equilibrium coupling position on the bone structure under a relatively small external force; and supporting means ilrmly mechanically coupled to the driving portion for holding said driven portion with the contactor in engagement with said said driving portion and said supporting means when said unit is actuated by the electrical means for transmitting the vibrations oi.' the contactor through the bone structure to the inner ear; the mass of said driving portion being only a small fraction of the mass of the body of said vbone structure, and being sumciently large and sumdevice, a vibratory unit sutliciently light andv small enough for comfortable and substantially inconspicuous wear coupled to a hearing inducing -bone structure oi' the user and comprising a driving portion, a driven portion and intermediate relatively-stm elastic elements interconnecting said driving and driven portions so as to permit a limited vibratory movement between at least parts oi' both portions; electrical means secured to said driving portion for actuating said portions throughout the principal speech irequency range and producing corresponding vi-v brations between said portions: a casing forming part oi' said unit and secured to said driving portion: a contactor directly secured to said driven portion for engaging the bone structure of the user; said contactor forming at least part of a wall oi said casing having a. wall portion with lateral dimensions sumciently extended and so arranged under the driving portion as to maintain said vibratory unit in a stable equilibrium coupling position on the bone structure unv.der a relatively small external force: and supporting means iirmly mechanically coupled to the driving portion for holding said driven portion with the contactor in engagement with said bone so that the contactor vibrates relatively to said driving portion and said supporting means when said unit isactuated by the electrical means tor transmitting the vibrations of the contactor through the bone structure to the inner ear; the mass oi said driving portion being only a small fraction of the mass or the body of said bone structure, and being sumciently large andl sutilciently actuated by said electrical means as to impart to said driven portion and, through its contactor to the bone. the vibratory energy required for inducing intelligible hearing of speech by bone conduction.

` 8. In a wearable bone conduction hearing aid device; a vibratory unit suillciently light `and small enough for comfortable and substantially inconspicuous wear coupled to a hearing inducing bone structure oi' the user and comprising a driving magnetic portion, a driven magnetic portion and intermediate relatively-sti!! elastic elements interconnecting saidfdriving and driven portions vibrate; electrical means secured to one of said portions for actuating said portions throughout the principal speech frequency range and producing corresponding vibrations between said portions; a casing forming part of said unit and secured to said driving portion; a contactor directly secured to said driven portion for engaging the bone structure of the user; said contactor forming at least part of a wall of said casing having a wall portion with lateral dimensions suilciently extended and so arranged under the driving portion as to maintain said vibratory unit in a stable equilibrium coupling position on the bone structure under a relatively small external force; and supporting means firmly mechanically coupled to the driving portion for holding said driven portion with the contactor in engagement with said bone so that the contactor vibrates relatively to said driving portion and said supporting means when said unit is actuated by the electrical means for transmitting the vibrations of the contactor through the bone structure to the inner ear; the mass of said driving portion being only a small fraction of the mass of the body of said bone structure, and being sufliciently large and sulliciently actuated by said electrical means as to impart to said driven portion, and through its contactor to the bone, the vibratory energy required for inducing intelligible hearing of speech by bone conduction.

9. In a wearable bone conduction hearing aid device, a vlbratory unit sufilciently light and small enough for comfortable and substantially inconspicuous wear coupled to a hearing inducing bone structure of thequser and comprising a driving portion, a driven portion and intermediate relatively-stm elastic elements interconnecting said driving and driven portions so as to permit a limited vibratory movement between at least parts of both portions; said driving and said driven portions having elements forming part of a magnetic structure including a magnetic gap across which said portions vibrate; electrical means secured to said driving portion for actuating said portions throughout the principal speech frequency range and producing corresponding vibrations between said portions; a casing forming part of said unit and secured to said driving portion; a contactor directly secured to said driven portion for engaging the bone structure of the user; said contactor forming at least part of a wall of said casing having a wall portion with lateral dimensions sufciently extended and .so arranged under the driving portion as to maintain said vlbratory unit in a stable equlibrium coupling position on the bone structure under a relatively small external force; and supporting means rmly mechanically coupled to the driving portion for holding said driven portion with the contactor in engagement with said bone so that the contactor vibrates relatively to said driving portion and said supporting means when said unit is actuated by the electrical means for tran;- mitting the vibrations of the contactor through the bone structure to the inner ear; the mass of said driving portion being only a small fraction of the mass of the body of said bone structure, and being sufllciently large and suilciently actuated by said electrical means as to impart to said driven portion, and through its contactor to the bone, the vibratory energy required for inducing intelligible hearing of speech by bone conduction.

LIEBER PATENTS CORPORATION.

Assignee of Hugo Lieber, Deceased, By CHARLES P. FRANCHOT,

President. 

